PET/CT scan or Positron Emission Tomography is a “sugar” scan. That is to say, it is a scan that shows where sugar is being used by the body. The CT part of the scan improves the image quality for the radiologist by adding more detail about the location of the findings within the body. The PET portion of the study requires an injection of sugar tagged with a radioactive tracer. After a 45 to 60 minute delay, the PET scan is performed in a doughnut shaped machine that looks something like a CT scanner. The CT scan is performed on the same machine at the same time. A computer fuses the PET and CT images together for reading by the radiologist.
PET/CT scans are used to find tumors. They may help in diagnosing tumors or checking the extent of spread of a tumor. They may also tell how well a tumor is responding to treatments. Most tumors use more than twice as much sugar as normal tissues like muscle, bone, skin and fat.
PET/CT scans can also be used to evaluate the brain for seizure disorders, tumors, memory problems and infection. The risk of injury from the dose of administered radioactive material is very low. No significant adverse effects of diagnostic levels of injected radioactive materials have been reported over decades of use.
You will receive special instructions when you schedule for your exam. You will be expected not to eat or drink types of foods containing sugar for several hours before the exam. It is important not to vigorously exercise before your exam or even run from the car if you are late for your study. If you are a diabetic you may receive additional instructions. Be sure to bring a list of your medications to your exam.
If you are possibly pregnant or breast feeding you should inform your doctor and the technologist at the time of the exam. You may need to reschedule or to pump and store breast milk before your study. You should not breast feed for at least a day or two after PET/CT scanning.
You may or may not change into an examination gown. All metal objects such as jewelry should be removed if possible. You may have your blood sugar checked to see if it is within acceptable range for the study with a skin prick blood tester. If your blood sugar is too high at the time of the exam you may have to reschedule for a later time or even a different day so that the scan results will be accurate. Most people who follow the preparation instructions will be well within the blood sugar range for scanning.
You will have an injection of a small amount of radioactive tracer (the sugar) in an arm vein before scanning. After about 60 minutes or so you will then have your PET and CT scans. The scan takes just a few minutes and is performed using a doughnut shaped machine that looks somewhat like a CT scanner.